ISTANBUL — Syrian rebel commanders said Thursday that they were disappointed in the Trump administration's decision to end a covert CIA weapons and training program for opposition fighters, an initiative that began under President Barack Obama but that fizzled out amid battlefield losses and concerns about extremism within rebel ranks.

"We definitely feel betrayed," said Gen. Tlass al-Salameh of Osoud al-Sharqiya, a group affiliated with the Free Syrian Army. Salameh and his deputies say that they have received CIA support to rout the Islamic State from areas of eastern Syria but that they have also fought battles against pro-government forces.

"It feels like we are being abandoned at a very difficult moment," Salameh said. "It feels like they only wanted to help when we were fighting [the Islamic State]. Now that we are also fighting the regime, the Americans want to withdraw."

Salameh and others, reached by phone Thursday, said they had only read about the decision, which was first reported by The Washington Post, in reports translated by local news media. The commanders were unclear how the policy to end the program would be implemented, or if their own fighters would be affected.

Others pointed to President Donald Trump's warming relations with Russia, which is a staunch backer of Syrian President Bashar Assad. Both the U.S. and Russian governments have said the priority is to fight the Islamic State.

"The picture is not clear for us yet, but I think it is a very bad move," Col. Ahmed al-Hammadi, an FSA commander in the Damascus countryside, said of the decision.

"It will give a boost to the Assad regime and strengthen the Iranians," he said, referring to Iran's substantial support for Assad. "And it will weaken America's influence in Syria and the region."

But it also put an official end to what analysts say had become an ineffective and largely defunct program, blunted by Russia's military intervention to prop up the Syrian regime in 2015, which dealt a devastating blow to the rebels.

"The weapons and resources the CIA provided were very little when compared with what Russia and Iran have sent to the regime," Salameh said.

"It made a difference, but not a massive one," he said of the CIA support. "It's not like the U.S. is sending us planes or ground troops."

The Obama policy was, in fact, designed to provoke a battlefield stalemate - which the administration hoped would lead to a negotiated end to the conflict. It began in 2013, with training and weapons for rebels vetted for extremist ties. This included groups such as northern Syria's Division 13 and the Yarmouk Army in the south, and they put Assad on the back foot.

But then Russia intervened with warplanes and battleships, and with the United States focused on the Islamic State, the rebels have struggled ever since.

"The program played an important role in organizing and supporting the rebels," said Lt. Col. Ahmed al-Saud, who commands the Division 13 rebel group in Idlib province.

He said that "this won't affect our fight against the regime, the Islamic State or Nusra," which is the former name of Syria's al-Qaeda affiliate. But he also expressed disbelief that the United States would end its support.

"I don't think this is going to happen," he said. "America is a superpower. It won't just retreat like that."